I disagree with Mr Mitchell. To my mind there are already quite enough restrictions on experimentation using human subjects. Sure, you can use other mammals such as mice, monkeys and so forth for a lot of basic safety experiments. But they don't tell you much about how a given drug is going to behave in a real life human being.

Ethics committees are very strict these days: I doubt the Milgram experiment would be allowed nowadays, for instance. But, still, some experiments on willing subjects – or "participants" as they're usually called these days – are needed because they provide essential information that could not be gathered by any other means.

In the case of ketamine, the drug's effect on the brain was believed to mimic one of the symptoms of schizophrenia – the hallucinatory sensation that external objects are joined to the body. Using ketamine on volunteers might have pointed researchers in the direction of the receptors in the brain which are involved in this "mislocalisation". Not only that, but the research had an unexpected outcome: one participant with an undeclared mental illness felt unaccountably cheery after the experiment. Maybe this is a chance effect. But possibly it points to some antidepressant benefit of ketamine itself.